Galaxies

1. Most galaxies are easily viewed with the naked eye.

Most galaxies are so far away that people can view them only with the
help of telescopes. Only three galaxies can be seen with the unaided eye:
the Andromeda Galaxy and the Large and Small Magellanic Clouds. These galaxies
appear as cloudy patches in the sky. Other galaxies appear as fuzzy spots
in the sky when viewed with small telescopes.

2. All galaxies are the same.

The shapes of galaxies vary – some are elliptical, others are spiral, and still others have no definite shape. Galaxies differ in color, composition, orientation, age, size, the number of stars within them, and their distance from Earth.

3. Galaxies are composed of stuff that is different from stars.

Galaxies are large collections of stars, gas, and dust held together by their gravitational attraction.

4. Galaxies are static, remaining unchanged with time.

In fact, galaxies are dynamic and change over millions of years. Stars are born and die in galaxies. A galaxy also can interact with another galaxy, which alters both galaxies' shapes.

5. You can judge the distance of a galaxy based on its size.

The size a galaxy appears to be to an observer depends on how many stars are in it and how far away it is. Two galaxies may appear to be the same size. One of them, however, may be a small galaxy close to Earth and the other a large galaxy that is much farther away.